Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 300921

Area Forecast Discussion
National Weather Service Sioux Falls SD
421 AM CDT MON MAY 30 2016

.SHORT TERM...(Today and Tonight)
Issued at 420 AM CDT Mon May 30 2016

Showers and thunderstorms gradually moving across the area early
this morning. A few storms have produced some heavy rainfall and
near severe hail...more than likely. The mid level wave responsible
for this convection will move through the area by about mid morning,
so will have the chance for thunderstorms mainly east of interstate
29 this morning with decreasing chances through about 16z. In the
wake of this wave, broad southerly flow will develop. Not easy to
discern when the better chance for convection will be. Thinking that
the first chance will be from late morning into the early afternoon
as the 850mb to 700mb winds quickly increase as low pressure deepens
over western north dakota and eastern montana. This might allow
scattered thunderstorms to develop and lift northward but the severe
threat with these storms should not be high as a potential lack of
moisture in this layer might keep instability a bit on the low side.
Will have a small chance for thunderstorms lifting from near the
Missouri River into east central South Dakota from about 17z through

After this deeper moisture, better instability and shear are in
place in central South Dakota by late afternoon and expect
thunderstorms to develop in this area. Initially the soundings
appear to point towards isolated to scattered stronger cells with
shear not too strong but well balanced and definitely supportive of
severe convection, especially with the potential for about 2000 j/kg
surface based CAPE. By mid evening a strong surge of mid level winds
from the west and the approach of the wave should increase moisture a
bit which will likely lead towards a better chance for a somewhat
organized line which would get to Interstate 29 about 10 pm and into
southwest Minnesota and northwest Iowa between 10 pm and 1 am. Hail
to the size of golf balls and 70 mph winds will be possible with
the initial development while winds to 70 mph will still be possible
farther east into the evening the threat for hail should drop to
half dollar.

.LONG TERM...(Tuesday through Sunday)
Issued at 420 AM CDT Mon May 30 2016

Assuming the organized nature of convection from Monday night, much
if not all of this may have progressed eastward out of the CWA,
leaving perhaps parts of southwest Minnesota and northwest Iowa with
lingering showers and a few rumbles of thunder. Upper low will
continue to wobble across North Dakota through the day, with jet
energy gradually intensifying through downstream quadrants. This
will cause Q vector convergence to linger somewhat over eastern
portions of the CWA. For the most part, will probably only see a few
lighter showers and more of a stalling to clearing. Fairly strong
dry slot will rotate through southeast South Dakota, at least at
lower levels. With good westerly component, enough mixing to expect
a recovery in temperatures to reach the mid 70s, versus potentially
some lower 70s in cloudier areas to the east/southeast. Along with
upper trough axis pushing into the far west toward evening, there
will likely be a small amount of convergence, and despite limited
moisture, there looks to be potential for a very small degree of
instability in a very narrow axis.  Have included a minimal chance
for showers and thunder around the K9V9 and KHON, but should be very
short window ending by sunset as boundary progresses into the area.

As secondary front barrels through on Tuesday night, northwest winds
will increase, and become quite breezy heading through much of
Wednesday.  Wednesday certainly the coolest day of the next week,
with mixing suggesting mid 60s to lower 70s. Coolest readings likely
where clouds will be more prevalent around southwest Minnesota. If
not for a very strong subsidence signal, would think could get a few
short showers across mainly southwest Minnesota, but have elected to
keep dry this go around. Chilly night will bring Thursday morning
lows into the mid to upper 40s for most.

Surface ridge at the heart of the chill will begin to shift off to
the east Thursday, returning southerly flow to the area. Thursday
will be very pleasant with low humidity and mild temperatures.
Elevated instability push by evening could bring an isolated shower
or thunderstorm, which may linger into early Friday for southwest
Minnesota and northwest Iowa. Stronger precipitation threat on
Friday night, as wave in northwest flow digs and pushes a decent
frontal boundary through the area. GFS is by far the most amplified
to digging and more threatening both shear/instability wise, but
even lesser digging ECMWF/Canadian do present a threat for a few
stronger storms along the boundary around Friday evening.

Amplification of the eastern trough/western ridge pattern should
push the area into a slightly cooler regime toward the start of
next week after a seasonably warm first weekend of June.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1037 PM CDT Sun May 29 2016

primarily VFR conditions are expected through the TAF period,
however scattered thunderstorms may develop across portions of the
area overnight. This activity will affect mainly the KFSD and KSUX site.


.FSD Watches/Warnings/Advisories...


LONG TERM...Chapman
AVIATION...JM is the U.S. government's official web portal to all federal, state and local government web resources and services.